Chroma tin as "Ilcrctlifiirt/ Substance*' SSI 



these plants. That the production of cilia is the main if not 

 the exclusive office of the body in these and other plants, Web- 

 ber and other observers have made certain. The question of 

 the relation of this body to the centrosonie, which latter is gen- 

 eral Iv held to be part of the nuclear-divisional apparatus of the 

 cell, has been much discussed. In the plants mentioned Web- 

 ber believed, seemingly with full justification, that the blepharo- 

 plast arises de novo in the cytoplasm and at no time has con- 

 nection with any part of the division apparatus. It seems to 

 have no office other than that of producing the cilia. Almost 

 certain it is, consequently., that in several distinct groups of 

 plants. Ginkgo, cycads and mosses for example, the main por- 

 tion of the motile organ of the- sperm cell is derived from the 

 cytoplasm of the cell and not from chromatin or any other 

 nuclear material. 



But such an origin does not hold for the corresponding organ 

 of all sperm cells. In several animals, insects and salamanders 

 for example, there is practical agreement among authorities that 

 the axial filament of the sperm "tail" grows out from the 

 centrosome. 2 Furthermore, it seems to be accepted that in 

 some animals, e.g.. some echinoderms and worms, the centro- 

 some arises from the nucleus.' Viewing these facts in connec- 

 tion with the recent tendency to exalt the nucleus as the "seat" 

 >f all sorts of cell capacity, and putting them alongside those 

 >\e sketched concerning the nuclear connection of flagella in 

 ic cilia-bearing proto/oans, one readily sees the strong temp- 

 iion to homologi/e the motor apparatus of the spermatozoan 

 (h that of the protozoan and conceive a common basis for both 

 the nucleus. If the centrosome could be held to have arisen, 

 ivlogeiictically, from nuclear chromatin; and if the blepharo- 

 plast, which is unquestionably a cilia-producer, could be counted 

 as fundamentally a centrosomal structure; and could such a 

 generalization be established, it would certainly be a considerable 

 achievement in support of the theory of universal nuclear and 

 chromatinic hegemony in development. We must, consequently, 

 scrutini/.e somewhat closely the evidence which points in this 

 direction. 



Eritlcnce from Certain (V//.v of M ulliccll/ilar Oryanixmx 



A decade ago the centrosome problem held a commanding 

 place in cytological investigation ami an extensive litera- 



